![]() Thus, data volumes are designed to persist data independently of the life of the container. This directory is not tied to the lifetime of the container itself, and the directory is managed by Docker and isolated from the core functionality of the host machine. When code in the container has access to the directory, that access is actually to a directory on the host OS. Volumes are directories mapped from the host OS to directories in containers. The following provides more detail about these options: If you need more information about storage in containers check on Docker storage drivers and About storage drivers. However, using Docker Volumes is now the preferred way to handle local data in Docker. ![]() Therefore, while it's possible to save the state of a container within its local storage, designing a system around this would conflict with the premise of container design, which by default is stateless. If the container is deleted from the system, those changes are lost. That information is "on top" of the original image on which the container is based. ![]() This Docker feature implements a copy-on-write task that stores updated information to the root file system of the container. Remote relational databases like Azure SQL Database or NoSQL databases like Azure Cosmos DB, or cache services like Redis. Tmpfs mounts are like virtual folders that only exist in the host's memory and are never written to the filesystem.Īzure Storage, which provides geo-distributable storage, providing a good long-term persistence solution for containers. Volumes are stored in an area of the host filesystem that's managed by Docker.īind mounts can map to any folder in the host filesystem, so access can't be controlled from Docker process and can pose a security risk as a container could access sensitive OS folders. The following solutions are used to manage data in Docker applications: ![]() If they're managed with a container orchestrator, you should assume that they might get moved from one node or VM to another. You should assume that container images, like processes, have multiple instances or will eventually be killed. While a container can write to its local storage, assuming that an instance will be around indefinitely would be like assuming that a single location in memory will be durable. A process doesn't maintain persistent state. In most cases, you can think of a container as an instance of a process.
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